[FFmpeg-user] Identifying an MP4 file
Carl Eugen Hoyos
cehoyos at ag.or.at
Thu Mar 31 23:54:24 CEST 2016
Sreenath BH <bhsreenath <at> gmail.com> writes:
> We have a HTTP Live Streaming (HLS) setup where we transcode
> incoming video files to H264 video and AAC audio and build
> playlist files from that. We want to avoid this step if the
> input file is already a MP4 file.
This is difficult to understand:
HLS uses mpeg-ts, mp4 is a different container.
> I know that MP4 is just a container and does not imply H264
> and AAC.
This is correct.
> I am planning to check the audio and video codec IDs in our
> program after getting the stream information using
avformat_find_stream_info tells you about the codecs used in
the stream, it does not tell you which container the stream
has (this has to be determined before).
> So, if the video codec ID and Audio codec ID are respectively,
> AV_CODEC_ID_H264 and AV_CODEC_ID_AAC
> Is it sufficient to qualify it as a MP4 file?
No, because H264 and AAC can be found in (many) other containers.
> The reason I ask is that there are some flv files that use
> the same codecs, but I am not sure if it would be safe it
> to treat it on par with an "authentic" mp4 file.
An flv and an mp4 file are definitely two different things.
(While an f4v file is an mp4 file.)
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