免费转换 MTS 文件

What is MTS format and why do camcorders use it?

MTS (MPEG Transport Stream) is video format used by AVCHD camcorders - consumer HD cameras from Sony, Panasonic, Canon, and others since 2006. AVCHD specification chose Transport Stream container (same as broadcast TV uses) for consumer video recording because TS's error resilience protects recordings from corruption if camera loses power, memory card fails, or recording is interrupted. Camcorders record to flash memory or hard drives that can experience write errors - TS's packet structure and error correction ensure partially-written files remain playable. Alternative containers (MP4, MOV) risk complete file loss if recording interrupted. AVCHD prioritized reliability over file size for consumer cameras capturing irreplaceable moments.

MTS files contain H.264 video (1080i or 1080p) and Dolby Digital AC-3 audio compressed efficiently for HD recording. File extension .mts distinguishes AVCHD recordings from other TS files (broadcast recordings use .ts). Camcorders organize MTS files in specific folder structure (BDMV/STREAM/) mimicking Blu-ray disc layout because AVCHD was designed for easy burning to Blu-ray. You can theoretically put SD card from camcorder into Blu-ray player and watch recordings directly. This compatibility was marketing feature though rarely used in practice - most people transfer to computer for editing and sharing. Modern camcorders increasingly use MP4 instead of MTS because smartphone generation expects .mp4 files that play everywhere without conversion.

How do I convert MTS files from my camcorder to MP4?

Multiple reliable conversion methods available:

HandBrake - GUI Conversion

HandBrake handles MTS conversion excellently with automatic settings detection. Open MTS file, HandBrake recognizes AVCHD structure, select MP4 output format, choose preset (HQ 1080p30 Surround for HD camcorder footage), click Start. HandBrake preserves 1080p resolution, converts H.264 video efficiently, and handles AC-3 audio appropriately. For batch conversion, add multiple MTS files to queue processing all overnight. Preview output confirming quality is acceptable - camcorder footage quality varies dramatically by lighting conditions and camera settings.

FFmpeg - Command Line

FFmpeg alternative for command-line users: `ffmpeg -i input.mts -c:v libx264 -crf 18 -c:a aac -b:a 192k output.mp4` transcodes to H.264/AAC with high quality. Since MTS already contains H.264, you can use stream copy avoiding re-encoding: `ffmpeg -i input.mts -c:v copy -c:a aac output.mp4` copies video losslessly, converts AC-3 audio to AAC. This is fast and maintains original video quality perfectly. However, AC-3 audio in MP4 has compatibility issues with some devices, so transcoding audio to AAC ensures universal playback.

Common Issues

Interlaced footage (1080i) needs deinterlacing for smooth playback on progressive displays. HandBrake's Decomb filter handles this automatically. Some camcorders split long recordings into multiple MTS files (2GB or 4GB chunks due to FAT32 file system limits). Concatenate before converting: `ffmpeg -f concat -safe 0 -i filelist.txt -c copy output.mts` where filelist.txt contains paths to all parts. Camcorder recordings often have variable frame rates which can cause audio sync issues - FFmpeg's `-vsync 1` fixes this.

Quality Settings

Use CRF 18-22 for transparent quality preservation (lower = better quality, bigger file). CRF 18 creates visually lossless output suitable for archival. CRF 22 provides excellent quality at smaller file size for everyday viewing. Avoid unnecessarily low CRF values (below 18) as they waste space without visible quality improvement. Test with small section first confirming settings work well for your specific footage before batch converting entire collection.

Choose HandBrake for simplicity and reliability, FFmpeg for automation and advanced control. Both produce excellent results when configured properly.

Why are MTS files larger than MP4 from my phone for same length video?

Several factors explain size difference:

Transport Stream Overhead

MTS uses broadcast-style container adding 5-10% overhead versus efficient MP4 container. Every 188-byte packet has headers, synchronization data, and padding that MP4 omits. This overhead protected recordings from corruption on camcorder but wastes space on computer. Additionally, camcorders often recorded at higher bitrates than necessary - 15-24 Mbps for 1080i when 8-12 Mbps H.264 delivers similar quality. Manufacturers prioritized quality over storage efficiency assuming users would transfer and delete recordings regularly.

Codec Evolution

Modern smartphones use HEVC (H.265) codec offering 40-50% better compression than H.264 used in older camcorders. Your phone's 1080p video at 10 Mbps HEVC looks better than camcorder's 1080p at 20 Mbps H.264. Codec evolution plus efficient MP4 container explains dramatic size difference. Converting old MTS files to modern HEVC in MP4 container can reduce size by 60-70% with minimal quality loss. However, HEVC encoding is slow and not all devices support HEVC playback.

Metadata and Audio

Camcorder MTS files often include multiple audio tracks (stereo and surround), recording metadata, and broadcast-style timestamps that phones don't capture. This extra data adds bulk without benefit for typical viewing. Converting MTS to MP4 strips unnecessary metadata and secondary audio tracks, keeping only essential video/audio. Size reduction comes from container efficiency, codec optimization, and metadata cleanup.

Bitrate Comparison

Check actual bitrates with MediaInfo or FFmpeg: `ffmpeg -i file.mts` shows video and audio bitrate. Camcorder MTS commonly uses 15-20 Mbps total bitrate while smartphone MP4 uses 8-12 Mbps. This explains 40-60% size difference even before considering container overhead. Modern encoders achieve same visual quality at lower bitrates through better compression algorithms and encoding profiles.

Container Efficiency

MP4 stores frames in variable-length chunks without padding, using space efficiently. TS's fixed packet size creates padding waste - if video frame is 1500 bytes, it requires 8 TS packets (1504 bytes total) with 4 bytes wasted. This inefficiency accumulates across entire file. Even without changing codecs, MTS to MP4 conversion saves 10-20% just from container overhead removal.

Recording Standards

AVCHD 规范（2006）反映了那个时代的存储成本和技术限制。制造商选择了保守的比特率和可靠的容器，优先考虑质量和可靠性而非效率。智能手机时代（2010+）伴随着丰富的存储，使得更高效的编码成为常态。不同年代的设计优先级解释了同一时期的格式为何具有不同的特性。

转换的好处

使用现代编码器（x264）将 MTS 转换为 H.264 MP4 可将文件大小减少 30-50%，同时保持视觉质量。转换为 HEVC MP4 可将大小减少 50-70%，但需要更多的处理时间，并且有兼容性折衷。根据播放设备的兼容性和所需的文件大小选择编码格式。对于大多数用户而言，H.264 MP4 提供了最佳的兼容性和压缩平衡。

由于容器开销、保守的比特率和较旧的编码器配置，MTS 文件较大。转换为现代 MP4 可回收浪费的空间，而不会造成明显的质量损失。

我可以直接编辑 MTS 文件，还是应该先转换？

专业视频编辑软件（Premiere Pro、Final Cut Pro、DaVinci Resolve）可以原生处理 MTS 文件，无需转换即可编辑。这些工具直接导入 AVCHD 文件夹结构，解析 MTS 文件，并提供完整的编辑功能。如果使用专业软件，可以直接编辑 MTS，保持原始质量，编辑后导出为所需格式。这避免了双重转码（MTS→MP4→编辑后的 MP4）导致的质量损失。专业工作流程：导入原生格式，无损编辑，一次导出为交付格式。

Consumer editors (iMovie, Windows Movie Maker, basic editing software) often struggle with MTS - poor scrubbing performance, audio sync issues, crashes. These editors expect MP4 and weren't designed for Transport Stream. If using consumer editing software, convert MTS to MP4 first using high quality settings (CRF 18-20), then edit converted file, export final result. This pre-conversion creates intermediate format that editor handles smoothly. Trade-off: conversion takes time and uses disk space, but editing experience is dramatically better.

替代方案：将 MTS 转换为适合编辑的编码格式（ProRes、DNxHD），适用于需要大量编辑、特效和调色的复杂项目。这些中间编码格式比 MTS 大，但优化了编辑性能（快速寻址，播放时 CPU 占用最小）和通过多次操作保持质量。编辑后，导出为 H.264 MP4 以便分享。这种三阶段工作流程（捕获格式 → 编辑格式 → 交付格式）是专业标准，确保质量和性能。普通用户可以跳过中间编码，直接编辑 MP4，接受小幅质量妥协以简化流程。

MTS 和 M2TS 之间有什么区别？

MTS 和 M2TS 都是 AVCHD 传输流文件，具有相同的内部结构——相同的视频、音频、编码器和容器格式。唯一的区别是上下文和文件扩展名。MTS（.mts 扩展名）指的是从摄像机录制的存储在 SD 卡、硬盘或内存棒上的录音，采用 BDMV/STREAM/ 文件夹结构。M2TS（.m2ts 扩展名）指的是在蓝光光盘或蓝光文件夹结构中的相同内容。AVCHD 摄像机创建 MTS；复制到蓝光以播放时使用 M2TS 命名。功能上是相同的——在扩展名之间重命名文件不会改变内容。

Technical specification: both use MPEG-2 Transport Stream container with H.264 video and AC-3 or LPCM audio. Both organized in BDMV folder structure with playlist files (.mpl), clip information (.clpi), and stream files. Camcorder recordings use MTS extension; Blu-ray discs use M2TS extension. This distinction was meant to clarify source (camera vs disc) but mostly creates confusion. Conversion tools treat them identically - HandBrake and FFmpeg handle both exactly the same way.

实际影响：无。使用相同的方法和设置转换 MTS 和 M2TS 文件。两者转换为 MP4 的方式相同，结果也相同。文件扩展名的区别是 AVCHD 规范的历史遗留物，试图保持蓝光兼容性。现代用户应忽略这种区别，将其视为同义词。如果您有这两种类型，批量将所有文件转换为 MP4，忘记 MTS/M2TS 的术语。扩展名不如理解您正在处理的 AVCHD 格式重要，该格式需要转换以实现广泛兼容。

为什么有些 MTS 文件在一个文件中包含多个视频片段？

AVCHD 摄像机将录制的内容组织为 MTS 文件中的片段，使用播放列表系统。相机创建连续的 MTS 文件，但维护播放列表（.mpl）以跟踪该文件中的每个场景。按下录制、停止、再次录制——摄像机将内容附加到同一个 MTS 文件，但创建播放列表条目标记每个片段的开始/结束位置。这允许高效存储（一个文件）和片段组织（播放列表提供访问点）。这类似于 DVD 中的章节——一个 VOB 文件，多个章节指向该文件中的时间戳。

将 MTS 导入计算机时，理解 AVCHD 格式的视频软件（Premiere、Final Cut）会根据播放列表信息显示单独的片段。不理解 AVCHD 的软件（简单转换器）将 MTS 视为单个连续视频，忽略片段边界。这让拍摄了 10 个独立片段的用户感到困惑，但转换却生成了一个长视频。解决方案：使用尊重播放列表的 AVCHD 识别软件，或在最终转换之前使用视频编辑器手动在所需位置拆分 MTS 文件。

Some camcorders also split recordings into multiple MTS files due to file system limitations. FAT32 (used on most SD cards) has 4GB file limit. Recording longer than ~20 minutes at HD bitrate exceeds 4GB, forcing camcorder to start new MTS file continuing recording. Camera firmware makes this seamless treating split files as one recording, but when transferring to computer you see multiple files (00001.MTS, 00002.MTS). Concatenate these files before converting: use FFmpeg concat demuxer or HandBrake's append feature to join seamlessly.

转换为 MP4 后，我应该保留原始 MTS 文件吗？

对于不可替代的内容（家庭视频、婚礼、一次性事件），保留原始 MTS 文件作为档案副本。MTS 包含完整的原始数据，包括所有音轨、元数据和最高质量。存储成本低——外部硬盘每千兆字节只需几分钱。保留原始文件可以为未来提供保障，以防出现更好的转换工具或需要重新编辑。使用 MP4 版本进行日常分享和播放，保持 MTS 档案以便保存。遵循 3-2-1 规则（3 份副本，2 种不同的媒体类型，1 份异地备份）备份这两种格式。

对于可替代或低价值的内容（随机镜头、测试录制、已经在其他地方备份的视频），在确认 MP4 转换成功后删除 MTS。观看转换后的文件，确认质量可接受且整个录制已被捕获。一旦满意，删除 MTS——没有必要囤积中间格式。许多用户积累了他们永远不会观看的摄像机录像的 TB 级数据。通过在转换后删除原始文件来整理收藏是数字卫生。保持 MP4 版本有序且易于访问；删除 MTS 杂乱。

折中方案：在转换后暂时保留 MTS 文件（6-12 个月）。这个宽限期允许发现转换问题或需要使用不同设置重新转换。在证明 MP4 版本运行良好并且您对此满意后，删除 MTS 文件以释放存储空间。这种延迟删除提供了安全网，而无需永久存储承诺。专业视频制作人永久保留摄像机原始文件；普通用户可以在验证期后删除。评估每个录制的价值并选择适当的保留政策。

我可以直接将 MTS 文件上传到 YouTube/Vimeo，还是必须先转换？

平台接受 MTS，但转换提供了优势：

直接上传支持

YouTube 和 Vimeo 直接接受 MTS 文件——这两个平台支持 AVCHD 格式的上传。它们的后台服务器会自动将上传内容转码为流媒体格式，无论源格式如何。您可以在不转换的情况下上传 MTS，平台会处理它。然而，由于较大的文件大小（传输流开销），MTS 的上传时间比等效的 MP4 更长。MTS 上传有效，但并非最佳选择。

质量考虑

上传最高质量源文件在平台转码后会产生最佳效果。如果您的 MTS 包含来自摄像机的原始 1080p60，直接上传 MTS，而不是先转换为较低质量的 MP4。平台从高质量源转码会产生比从已经压缩的中间文件转码更好的输出。然而，如果您打算在上传之前进行任何编辑，请将编辑后的结果导出为高质量的 MP4 并上传。

带宽节省

在上传之前将 MTS 转换为 MP4 可显著减少上传时间。MTS 文件比 MP4 大 5-10%，并且通常使用不必要的高比特率。转换为优化的 MP4（1080p 的 8-12 Mbps）可将文件大小减少 30-50%，这意味着在慢速互联网连接上更快的上传。如果您有千兆互联网，这无关紧要；在慢速连接上则显著。

本地副本的好处

在上传之前将 MTS 转换为 MP4 可为您提供可以在其他地方重用的本地副本（社交媒体、家庭分享、本地存储），并加快上传速度。上传原始 MTS 只有在您立即从相机上传而不保留本地副本并希望获得绝对最高质量时才有意义。对于大多数用户而言，预先转换为 MP4 提供了更好的工作流程——一个高质量的 MP4 文件在任何地方都可用。

实用工作流程

将 MTS 转换为高质量 MP4（CRF 18-20），创建母版副本。将此 MP4 上传到 YouTube/Vimeo。将相同的 MP4 用于其他分享需求。这一次转换创建了适合所有用途的通用兼容文件。不要上传 MTS 以为您在保留质量——平台无论如何都会转码，破坏原始文件。一次转换为良好的 MP4，随处使用。高效的工作流程胜过完美主义。

平台接受 MTS，但先转换为 MP4 提供了更快的上传、本地可重用副本和相同的最终质量。除非直接从相机上传，否则请转换。

为什么我的计算机上 MTS 录像看起来有交错的水平线？

许多摄像机录制的是 1080i（交错）而不是 1080p（逐行）。交错视频将每帧分成两个场（奇数/偶数行），每 1/60 秒捕获一次，从 30 帧生成每秒 60 个场。这是广播标准，摄像机继承了它。交错视频在旧的 CRT 电视上显示良好，但在现代 LCD 显示器和电视上显示出梳状伪影（水平线），而这些显示器是逐行显示的。您的计算机显示器无法正确显示交错内容，因此您会看到难看的线条图案，尤其是在运动中。

Solution: deinterlace during conversion to MP4. HandBrake's Decomb filter automatically detects and deinterlaces interlaced content converting to progressive. FFmpeg's yadif filter does same: `ffmpeg -i input.mts -vf yadif -c:v libx264 -crf 18 output.mp4` removes interlacing producing smooth progressive video. Quality of deinterlacing varies - simple methods halve vertical resolution, better algorithms (yadif, nnedi) interpolate missing lines preserving resolution. Modern deinterlacing is very good but can't fully recover progressive quality from interlaced source.

预防措施：更新的摄像机录制 1080p（逐行），完全避免了这个问题。如果购买二手摄像机或拥有旧相机的录像，请预期 1080i 需要去交错。检查相机规格——1080i60 意味着交错，1080p30/60 意味着逐行。有些相机提供这两种模式；检查录制设置。一旦录像被捕获为交错，您就无法更改——在转换过程中去交错，接受小幅质量折衷。良好的去交错在典型观看情况下看起来不错；只有在与原生逐行比较时才会明显。

批量转换 MTS 录制为 MP4 的最佳工具是什么？

不同的工具适用于不同的转换需求：

HandBrake - 图形用户界面批处理

HandBrake 在批量视频转换方面表现出色，具有队列管理功能。拖动多个 MTS 文件，选择预设（标准录像的 HQ 1080p30，高帧率的 HQ 1080p60），将所有文件排队，过夜处理。预设优化质量和兼容性。适合在没有特殊要求的情况下转换摄像机库。免费、跨平台、积极维护。能够很好地处理 AVCHD 结构，包括拆分文件和播放列表。

FFmpeg - Automation

FFmpeg enables automated workflows through scripting. Write PowerShell script that processes entire folder of MTS files with consistent settings. Can integrate metadata extraction, subtitle processing, file organization. Steep learning curve but unlimited flexibility. Example script: find all MTS files, check if already converted, transcode with quality settings, organize by date, all automatically. Professional solution for serious library management.

Adobe Media Encoder

Adobe Media Encoder offers professional-grade batch conversion with extensive format support and preset library. Drag MTS files, select H.264 preset, customize settings if needed, export all. Watch folders enable automatic processing - drop MTS in folder, software converts automatically. Commercial software (subscription) but integrates with Premiere Pro for editing workflow. Professional reliability and quality.

Format Factory - Windows

Format Factory provides simple GUI for batch conversion on Windows. Add multiple MTS files, select MP4 output format, choose quality settings, start conversion. Free software with straightforward interface. Not as sophisticated as HandBrake but adequate for basic batch conversion without learning curve. Good option for non-technical users wanting simple batch processing.

文件组织

在批量转换之前，正确组织 MTS 文件。复制整个 BDMV 文件夹结构以保持组织。有些转换工具需要完整的 AVCHD 结构才能正确解析播放列表和片段信息。将单个 MTS 文件转换到文件夹结构之外可能会丢失片段边界或元数据。在处理整个库之前，先用少量文件测试转换工作流程。

质量验证

实施质量检查——随机抽样转换，观察音频同步、视频质量、没有丢帧、适当的去交错。没有验证的自动转换风险默默产生缺陷输出。批量处理放大了错误——一个错误的设置会毁掉整个集合。首先用小批量测试，彻底验证结果，然后扩展到完整库。量两次，切一次。

硬件编码

Modern GPUs accelerate H.264/H.265 encoding dramatically. FFmpeg with NVENC (NVIDIA), QuickSync (Intel), or VCE (AMD) transcodes 5-10x faster than CPU. HandBrake supports hardware encoding too. Enable if converting large libraries - time savings is enormous. Quality slightly worse than CPU encoding but difference negligible for camcorder footage. Hardware encoding makes batch conversion practical.

存储规划

在批量转换之前估算空间需求。MTS 转 H.264 MP4 通常节省 20-40% 的空间。MTS 转 HEVC MP4 节省 50-70%，但编码所需时间更长。计算 MTS 库的总大小，估算转换节省，确保输出有足够的磁盘空间。在确认转换成功之前，暂时保留这两种格式。

备份策略

在批量转换过程中保持备份。在验证 MP4 转换正常工作之前，不要删除所有 MTS 文件。分阶段处理库——转换一批，验证，删除原件，移动到下一批。这种分阶段的方法可以防止在转换设置错误时发生灾难性数据丢失。在处理不可替代的家庭视频时，安全总比后悔好。

元数据保留

AVCHD files contain recording metadata - date, time, camera settings. Preserve this metadata during conversion using tools that support metadata transfer. FFmpeg can copy metadata with `-map_metadata 0`. HandBrake preserves basic metadata. This information is valuable for organizing and searching video library by recording date. Don't lose metadata through careless conversion.

AVCHD 和蓝光之间有什么关系？

AVCHD（高级视频编码高清）规范是由索尼和松下设计的，以便与蓝光光盘格式兼容。AVCHD 使用相同的编码器（H.264 视频，AC-3 音频）、相同的容器（MPEG-2 传输流）和相同的文件夹结构（BDMV），与蓝光电影相同。这种兼容性意味着 AVCHD 录制可以直接刻录到蓝光光盘上，并在蓝光播放器中播放，无需转换。营销角度是“在摄像机上录制，刻录到蓝光，家庭影院观看”，创建了从捕获到分发的无缝工作流程。

BDMV 文件夹结构中的 MTS 文件本质上是蓝光格式，但存储在 SD 卡或摄像机硬盘上，而不是光盘。您可以将摄像机 SD 卡上的 BDMV 文件夹复制到蓝光光盘（使用适当的刻录软件），光盘将在蓝光播放器中播放。这在理论上是可行的，但在实践中很少使用——大多数人更喜欢上传到 YouTube 或转换为 MP4 以便在计算机上观看，而不是刻录物理光盘。蓝光刻录需要特殊的刻录机和空白光盘，与数字共享相比造成了摩擦。

AVCHD's Blu-ray compatibility became less relevant as physical media declined and streaming dominated. Format's legacy is organizational structure (BDMV folders, playlist system) that persists in MTS files even though nobody burns Blu-rays anymore. Understanding AVCHD-Blu-ray relationship explains why camcorder files use seemingly overcomplicated folder structure - it was designed for disc authoring workflow that never materialized for consumers. Today's relevance: none. Convert MTS to MP4 and ignore Blu-ray compatibility entirely.

How do I handle split MTS files from long recordings?

Camcorders split long recordings into multiple MTS files due to file system limitations. FAT32 (used on most SD cards) has 4GB maximum file size. Recording longer than 15-20 minutes at HD bitrate (15-20 Mbps) exceeds 4GB forcing camera to create new file. Camera firmware continues recording seamlessly across files - you press record once, camera creates 00001.MTS, 00002.MTS, 00003.MTS as needed. Camcorder's playback treats these as single recording, but when transferred to computer they appear as separate files requiring joining.

FFmpeg's concat demuxer joins split files perfectly: Create text file listing all parts: `file '00001.MTS'` `file '00002.MTS'` `file '00003.MTS'`. Then concatenate: `ffmpeg -f concat -safe 0 -i filelist.txt -c copy joined.mts`. This copies streams without re-encoding (fast and lossless). Then convert joined MTS to MP4: `ffmpeg -i joined.mts -c:v libx264 -crf 20 -c:a aac output.mp4`. This two-step process (join, then convert) ensures you don't lose any footage and maintain proper continuity.

HandBrake can't join files natively but you can manually append - convert first file, then use 'Queue' → 'Add Source' → 'Append', select next file, repeat for all parts. This queues conversion with all parts concatenated. Alternative: use video editor (Premiere, DaVinci Resolve) which imports AVCHD structure properly and handles split files automatically showing them as single clip. Professional editors understand AVCHD playlist system that links split files. Choose method based on tools available - FFmpeg for command-line, editor for GUI, both work reliably.

Why did smartphones kill the camcorder market?

Convenience trumped quality - smartphones always with you capture spontaneous moments that dedicated camcorder would miss. Having separate device requires planning, remembering to bring it, keeping it charged. Smartphone is always in pocket making casual video recording frictionless. Even if camcorder video quality is superior, convenience of instant capture and immediate sharing from smartphone outweighed quality advantages for most consumers. 'Best camera is the one you have with you' proved decisive. Camcorder market collapsed not because technology was bad but because usage model was wrong for smartphone era.

Sharing friction - camcorders captured to proprietary formats (MTS) requiring computer transfer and conversion before sharing. Smartphones capture MP4 directly uploadable to social media, messaging apps, cloud storage with zero friction. This immediacy matched social media era where sharing is primary purpose. Camcorder workflow (record → transfer → convert → edit → share) had too many steps. Smartphone workflow (record → share) eliminated friction. Younger generations never learned camcorder workflow; smartphones were their first video devices. Format compatibility and workflow simplicity matter more than technical specifications.

Good-enough quality - smartphone video quality improved dramatically 2010-2015 reaching 'good enough' threshold for casual use. 1080p from iPhone 6 (2014) satisfied most users even if camcorder's 1080p was technically better. Diminishing returns from quality improvements meant marginal camcorder advantages weren't worth separate device. Dedicated camcorders still have advantages (optical zoom, better low light, longer recording time, superior stabilization) but these matter only for enthusiasts. Mass market chose convenience over perfection. AVCHD/MTS represents camcorder era (2006-2015) that ended not from technological failure but from being disrupted by better usage model.

What happens to 5.1 surround sound when converting MTS to MP4?

MTS files from camcorders typically contain Dolby Digital AC-3 5.1 surround audio if camera had multiple microphones (some higher-end models). Converting to MP4, you have options: preserve AC-3 audio (compatibility issues on some devices), convert to AAC 5.1 (universal compatibility), or downmix to stereo AAC (smallest file, works everywhere). Most camcorder recordings have stereo audio despite being stored as AC-3 - camera encodes stereo source into AC-3 format without actual surround separation. True 5.1 requires camera with multiple directional microphones which consumer camcorders typically lack.

FFmpeg handles audio flexibly: Keep AC-3: `ffmpeg -i input.mts -c:v libx264 -c:a copy output.mp4` copies audio without conversion. Convert to AAC 5.1: `ffmpeg -i input.mts -c:v libx264 -c:a aac -ac 6 output.mp4` preserves channel layout. Downmix to stereo: `ffmpeg -i input.mts -c:v libx264 -c:a aac -ac 2 output.mp4` creates stereo mix. HandBrake offers similar options in Audio tab. Choose based on target playback devices - if watching on TV with surround system, preserve 5.1; if watching on phone/laptop, stereo is adequate and more compatible.

Practical recommendation: check if your camcorder actually captured true surround (test by listening to 5.1 output on proper system) or just stereo encoded as AC-3. Most consumer camcorders recorded stereo regardless of format. If stereo source, downmix to AAC stereo for universal compatibility and smaller file size. If genuine 5.1, convert to AAC 5.1 preserving surround while ensuring MP4 compatibility. Don't obsess over maintaining AC-3 format - AAC 5.1 sounds identical to AC-3 5.1 at appropriate bitrates (256-384 kbps) and has better device support.

What lessons does AVCHD/MTS teach about consumer video format decisions?

Reliability engineering matters for consumer devices capturing irreplaceable moments - AVCHD chose Transport Stream specifically for error resilience protecting recordings from corruption during camera failures. This was correct decision for camcorders where power loss or memory card errors could destroy precious memories. Format designers understood user needs (preserve family memories) and prioritized accordingly. Compare to professional formats which assume reliable equipment and environments. Consumer-focused formats require different priorities than professional formats. AVCHD got this right even though TS overhead seems wasteful in hindsight.

Industry standards create compatibility ecosystem - AVCHD specification (Sony/Panasonic collaboration) enabled interoperability between different manufacturers' cameras, editing software, and playback devices. Any AVCHD camera worked with any AVCHD software. This cooperation created consumer confidence and market growth. Contrast with modern smartphone video where each manufacturer uses slightly different implementations causing compatibility quirks. Standards-based approach benefits entire ecosystem even as individual companies sacrifice proprietary differentiation. AVCHD's industry-wide adoption demonstrates value of cooperation over competition.

Format evolution must balance legacy and progress - AVCHD served well 2006-2015 but became outdated as HEVC and MP4 offered better compression and compatibility. Format's Blu-ray compatibility (originally selling point) became irrelevant as streaming replaced physical media. Smartphones offering good-enough video quality killed dedicated camcorder market, and their native MP4 became de facto standard. AVCHD died not from technical failure but from market disruption. Lesson: formats designed for specific hardware ecosystems become obsolete when those ecosystems disappear. Design for flexibility and migration paths. AVCHD's clear conversion path to MP4 enabled users to preserve content even as format became legacy.