Changing PAR in H.264 bitstream using FFmpeg

Selur · 30th November 2019, 08:35

Using a file named 'h264_par_1.mp4' with the following characteristics:

h264_par_1 had:
Sampled_Width : 640
Sampled_Height : 352
Pixel aspect ratio : 1.000 <-
Display aspect ratio : 1.818
Display aspect ratio : 16:9

one can use:

Code:

ffmpeg -y -i "E:\Output\h264_par_1.mp4" -map 0:0 -vcodec copy -an -sn  -bsf:v h264_metadata=sample_aspect_ratio=2 "E:\Output\h264_par_2.mp4"

(seems to work fine with any x264 encode)
to change the PAR from 1 to 2.

h264_par_2 has:
Sampled_Width : 640
Sampled_Height : 352
Pixel aspect ratio : 2.000 <-
Display aspect ratio : 3.636
Display aspect ratio : 3.636

Problem is if the input stream has no PAR data like 'Attica The Movie - Trailer By Brass':
(which I uploaded to my GoogleDrive

Width : 1280
Width : 1 280 pixels
Height : 720
Height : 720 pixels
Pixel aspect ratio : 1.000
Display aspect ratio : 1.778
Display aspect ratio : 16:9
note: MediaInfo shows no Sampled Width/Height

Code:

ffmpeg -y -i "F:\TestClips&Co\files\MPEG-4 H.264\Attica The Movie - Trailer By Brass.mp4" -map 0:0 -vcodec copy -an -sn -bsf:v h264_metadata=sample_aspect_ratio=2 "E:\Output\test.mp4"

fails with

Code:

[AVBSFContext @ 000001bcad3b5b00] rbsp_alignment_zero_bit out of range: 1, but must be in [0,0].
[AVBSFContext @ 000001bcad3b5b00] Failed to read unit 0 (type 7).
[AVBSFContext @ 000001bcad3b5b00] Failed to read extradata.
Error initializing bitstream filter: h264_metadata

My current guess is that the original stream has no explicit PAR (/ Sampled Width/Height) info which is why ffmpegs bitstream filter can't modify those values and change the PAR.

-> Does anyone know a way to change the PAR of such a stream without reencoding (preferably with ffmpeg)?

Cu Selur

30th November 2019, 08:35	#1 \| Link
Selur Registered User Join Date: Oct 2001 Location: Germany Posts: 7,277	Changing PAR in H.264 bitstream using FFmpeg Using a file named 'h264_par_1.mp4' with the following characteristics: h264_par_1 had: Sampled_Width : 640 Sampled_Height : 352 Pixel aspect ratio : 1.000 <- Display aspect ratio : 1.818 Display aspect ratio : 16:9 one can use: Code: ffmpeg -y -i "E:\Output\h264_par_1.mp4" -map 0:0 -vcodec copy -an -sn -bsf:v h264_metadata=sample_aspect_ratio=2 "E:\Output\h264_par_2.mp4" (seems to work fine with any x264 encode) to change the PAR from 1 to 2. h264_par_2 has: Sampled_Width : 640 Sampled_Height : 352 Pixel aspect ratio : 2.000 <- Display aspect ratio : 3.636 Display aspect ratio : 3.636 Problem is if the input stream has no PAR data like 'Attica The Movie - Trailer By Brass': (which I uploaded to my GoogleDrive Width : 1280 Width : 1 280 pixels Height : 720 Height : 720 pixels Pixel aspect ratio : 1.000 Display aspect ratio : 1.778 Display aspect ratio : 16:9 note: MediaInfo shows no Sampled Width/Height Code: ffmpeg -y -i "F:\TestClips&Co\files\MPEG-4 H.264\Attica The Movie - Trailer By Brass.mp4" -map 0:0 -vcodec copy -an -sn -bsf:v h264_metadata=sample_aspect_ratio=2 "E:\Output\test.mp4" fails with Code: [AVBSFContext @ 000001bcad3b5b00] rbsp_alignment_zero_bit out of range: 1, but must be in [0,0]. [AVBSFContext @ 000001bcad3b5b00] Failed to read unit 0 (type 7). [AVBSFContext @ 000001bcad3b5b00] Failed to read extradata. Error initializing bitstream filter: h264_metadata My current guess is that the original stream has no explicit PAR (/ Sampled Width/Height) info which is why ffmpegs bitstream filter can't modify those values and change the PAR. -> Does anyone know a way to change the PAR of such a stream without reencoding (preferably with ffmpeg)? Cu Selur __________________ Hybrid here in the forum, homepage Last edited by Selur; 30th November 2019 at 08:37.